NEW DELHI (REUTERS) - Sri Lanka's security forces have used rape to torture and extract confessions from suspected Tamil separatists almost four years after the country's civil war ended, Human Rights Watch (HRW) said in a report on Tuesday.

The rights group documented 75 cases of predominately Tamil men and women who said they were held in Sri Lankan detention centres and repeatedly raped and sexually abused by the military, police and intelligence officials.

The victims - now living as asylum seekers, most of them in Britain - said once they confessed to being a member of the Tamil Tiger rebel group, the abuse generally stopped and they were allowed to escape by paying a bribe, before fleeing abroad.

"We found that rape was used to secure some sort of confession, but also as a political tool to punish people," Meenakshi Ganguly, the rights group's South Asia director, told a news conference in New Delhi.